export default {
    bind(el, binding, vnode) {
      const dialogHeaderEl = el.querySelector(".el-dialog__header");
      const dragDom = el.querySelector(".el-dialog");
      dialogHeaderEl.style.cssText += ";cursor:move;";
      dragDom.style.cssText += ";top:0px;";
  
      // 获取原有属性 ie dom元素.currentStyle 火狐谷歌 window.getComputedStyle(dom元素, null);
      const getStyle = (function () {
        if (window.document.currentStyle) {
          return (dom, attr) => dom.currentStyle[attr];
        } else {
          return (dom, attr) => getComputedStyle(dom, false)[attr];
        }
      })();
  
      dialogHeaderEl.onmousedown = (e) => {
        // 鼠标按下，计算当前元素距离可视区的距离
        const disX = e.clientX - dialogHeaderEl.offsetLeft;
        const disY = e.clientY - dialogHeaderEl.offsetTop;
  
        const dragDomWidth = dragDom.offsetWidth;
        const dragDomheight = dragDom.offsetHeight;
  
        const screenWidth = document.body.clientWidth;
        const screenHeight = document.body.clientHeight;
  
        const minDragDomLeft = dragDom.offsetLeft;
        const maxDragDomLeft = screenWidth - dragDom.offsetLeft - dragDomWidth;
  
        const minDragDomTop = dragDom.offsetTop;
        const maxDragDomTop = screenHeight - dragDom.offsetTop - dragDomheight;
  
        // 获取到的值带px 正则匹配替换
        let styL = getStyle(dragDom, "left");
        let styT = getStyle(dragDom, "top");
  
        if (styL.includes("%")) {
          styL = +document.body.clientWidth * (+styL.replace(/%/g, "") / 100);
          styT = +document.body.clientHeight * (+styT.replace(/%/g, "") / 100);
        } else {
          styL = +styL.replace(/\px/g, "");
          styT = +styT.replace(/\px/g, "");
        }
  
        document.onmousemove = function (e) {
          // 通过事件委托，计算移动的距离
          let left = e.clientX - disX;
          let top = e.clientY - disY;
  
          // 边界处理
          if (-left > minDragDomLeft) {
            left = -minDragDomLeft;
          } else if (left > maxDragDomLeft) {
            left = maxDragDomLeft;
          }
  
          if (-top > minDragDomTop) {
            top = -minDragDomTop;
          } else if (top > maxDragDomTop) {
            top = maxDragDomTop;
          }
  
          // 移动当前元素
          dragDom.style.cssText += `;left:${left + styL}px;top:${top + styT}px;`;
  
          // emit onDrag event
          vnode.child.$emit("dragDialog");
        };
  
        document.onmouseup = function () {
          document.onmousemove = null;
          document.onmouseup = null;
        };
      };
    },
  };